Analog "AUX" input has a very high pitched squealing noise when using RCA to 3.5mm cables connected to the rest of my equipment (tried multiple cables on both my Focusrite Saffire firewire DAC and Focusrite Scarlett USB DACs - multiple outputs).BTW - Not a ground loop buzz, no I didn't want to pass through another

It turns out the USB port on the AD-18 only works as an input to use the amp as an external sound card for a PC

It is a SDH 3.5mm to RCA that also works as an input for a second optical

The various inputs are great, the 5 way binding posts seem good

Bluetooth is a great feature as well as all the different inputs

The amp was loud enough and reasonably well made but all the magic and excitement t of the humble hybrid tube amp it was replacing had vanished